AIS transponder costs around $1400 (Aust), which imo makes it a better proposition than just installing a receiver. Will also have to install another VHF antennna. I think peace of mind comes in knowing that the big ships can see you as much as knowing what commercial shipping is around - we know they don't always see or even look on radar. Also an advantage in knowing the call sign of that ship heading your way from the horizon.
A display in the cockpit runs at around 3 amps or less I believe, while a laptop may draw twice that much. The AIS unit itself draws very little power. I will use the laptop for passage planning and as a chartplotter backup only.